Fuel injection idle enrichment control mechanism



E s DAHL 3,064,636

FUEL macnou IDLE ENRICHMENT CONTROL MECHANISM Filed Dec. 22, 1960 Nov.20, 1962 Cit United rates Fatert This invention relates to an idlecontrol mechanism for a fuel injection system. that is adapted toincrease or enrich the output of a fuel injection pump during idleconditions of the engine.

In internal combustion engines of the reciprocating piston type, it isnecessary to enrich the fuel supply during idle condition primarilybecause of exhaust gas dilution. This enrichment is necessary oncarbureted engines as well as on engines equipped with fuel injection.

When an internal combustion engine is operating at idle, the throttlevalve is almost completely closed, and the pressure within theair-intake manifold is comparatively low. The pressure within acombustion chamber during an exhaust stroke, however, is close toatmospheric pressure.- When the air-intake valve opens, a portion of theexhaust gas remaining in the cylinder expands into the air-intakemanifold. During the remainder of the intake stroke, the exhaust gas issucked back into the combustion chamber before a mixture of fresh airand fuel enters the chamber. To offset the effects of the inert exhaustgas which dilutes the explosive mixture, the fuel-to-air ratio must beincreased or enriched. The amount of enrichment necessary is a functionof idle speed and valve overlap. When the throttle valve is opened, thepressure within the air-intake manifold rises and the effect of exhaustgas dilution is diminished. The proportion of fuel supplied thereaftershould be decreased to maintain the proper fuel-to-air ratio.

It is an object of the present invention to provide a control mechanismadapted to exert a metering bias force on a fuel injection controlsystem during idle conditions, and adapted to completely remove thisbias force when the throttle valve is moved slightly beyond the idleposition.

It is a more particular object to provide a control mechanism adapted tocontrol the output of a fuel injection pump including a servomotorresponsive to a differential pressure developed at the throttle valvefor exerting a bias force on the control mechanism during idlecondition.

It is a still more particular object to provide a control mechanism fora fuel injection pump including a movable cam adapted to control theoutput of the pump, a manifold pressure responsive servomotor for movingthe cam,

and a differential pressure servomotor responsive to a.

differential pressure developed across the throttle valve and effectiveto exert a bias force on the manifold pressure servomotor during idlecondition, but not when the throttle valve is opened slightly beyond theidle position.

The invention consists of the novel constructions, arrangements, anddevices to be hereinafter described and claimed for carrying out theabove-stated objects and such other objects as will appear from thefollowing de scription of a prefered form of the invention, illustratedwith reference to the accompanying drawings, wherein:

FIG. 1 is a schematic view, partially in section, of the improvedcontrol mechanism of the present invention; and

FIG. 2 is a graph of the air-fuel ratio supplied to an opening.

same result.

3,964,636 Patented Nov. 20, 1962 ice Description Referring to FIG. 1,the complete control mechanism is designated generally by the numeral 10and is adapted to control the output of a fuel injection pump 11. Themechanism 10 comprises a computer or integrator section 12, a manifoldpressure responsive servomotor 13, an idle enrichment servomotor 14, anda throttle body 15.

The fuel injection pump 11 includes a metering valve or shuttle 16 andis adapted to supply metered charges of fuel to the various enginecylinders in sequence with the opening of the respective intake valves.

The computer section 12 comprises a casing 19 attached to the pump 11, amovable cam 20 having a cam surface 21, a cam follower 22 in contactwith the cam surface 21, and a cam follower arm 23. The cam 20 isattached to a connecting shaft 24 of the manifold pressure respon Thecam follower 22 is rotatably' mounted on a pin 25 carried by the arm 23,and the' arm 23 is pivotally disposed on a pin 26 mounted in the casing19. A connecting link 27 is disposed between sive servomotor 13.

the cam follower arm 23 and the metering valve 16 of the pump 11. Thelink 27 is moved longitudinally by' the cam follower arm 23 forcontrolling the output of the pump 11 as the cam 29 is movedlongitudinally under the influence of the servomotor 13.

The manifold pressure responsive servomotor 13 com-j prises a casing 39formed with an internal chamber 31, a

flexible diaphragm 32, a spring-retaining cup 33, and av spring 34. Thespring-retaining cup 33 and diaphragm 32' are attached to the connectingshaft 24 by means of a screw 35. The casing is attached to the casing 19and is formed with a port 36 opening into the chamber 31. The port 36 isconnected by means of a conduit 37 to a port 38 in the air-intakemanifold 39.

The idle enrichment servomotor 14 comprises a casing 40 formed with aninternal cavity 41, a flexible diaphragm of machine screws 45.

port 49 in the throttle body 15. v The throttle body 15 comprises an air52 is disposed in an air passage 54 and is the primary control valve forregulating the amount of air entering the air-intake manifold 39. Theair-bleed control valve 53 comprises a casing portion 55 formedintegrally with.

the casing 15, a threaded needle valve 56, and a spring 57. The casingportion 55 is formed with an internal.

cavity 58 into which the port 49 opens and into which i The cavity 58 isconnected the needle valve 56 extends. by means of a channel 59 to aport 60' in the wall of the air passage 54 at a point downstream orbelow the air throttle valve 52. The cavity 58 is also connected bymeans of a port 61 to the air passage 54 at a point slight- 1y above theair throttle valve 52. The port 61 is adapted to be restricted by apoint 62 on the needle'valv'e 56. I It is contemplated that the port 60may be restricted by 1 still obtain the the valve 56 instead of the port61 and Operation In operation, the control system 10 functions tocontrol the output of the pump 11 as follows: Y

When the engine is running, the pressure within the airhorn or casing 50attached to the air-intake manifold 39, a large air throttle valve 51, asmall air throttle valve 52, and an I air-bleed adjustment valve 53. Thesmall throttle valvell intake manifold 39 is less than atmosphericpressure and this pressure is transmitted through the conduit 37 to thecavity 31 of the servomotor 13. A differential in pressure betweenmanifold pressure, and atmospheric pressure is developed across thediaphragm 32. The force due to this differential in pressure tends toforce the connecting shaft 24 and cam 20 to the left, as shown, againstthe action of the spring 34 and thereby tends to reduce the output ofthe fuel injection pump 11. The differential in pressure is determinedby the speed of the engine and the, degree of opening of the throttlevalves 52 and 51.

' During idle conditions, both of the throttle valves 52 and 51 aresubstantially closed, the pressure within the air-intake manifold 39 iscomparatively low, and the force due to the differential in pressureacross the diaphragm 32 is comparatively large. The cam 20, therefore,is moved to the left tending to reduce the outputrof the pump 11.

As pointed out above, it is necessary to enrich the fuel output duringidle condition to compensate for exhaust gas dilution. The need for thisenrichment is illustrated by the graph of FIG. 2 which is a plot of theair-fuel ratio demanded by an internal combustion engine as a functionof effective throttle opening. The upper curve on the graph shows theair-fuel demand of a multi-cylinder engine with poor distribution andthe air-fuel ratio required at idle is indicated by the letter A. Thelower curve illustrates'the air-fuel ratio demand of an ideal engine.The demand of an engine equipped with fuel injection approaches theideal because of its superior distribution. However, even for the idealengine, considerable enrichment at idle is required, as indicated at A,because of exhaust gas dilution.

A bias force to produce the necessary enrichment during idle conditionis provided by the servomotor 14. The bias force is developed by apressure differential across the area of the diaphragm 42. The pressureactingon the right side of the diaphragm '42 is the same as the pressureexisting within the cavity 31 of the servomotor 13, which, in turn, isthe same asthe pressure within the air-intake manifold 39. The pressureacting against the left side of the diaphragm 42 is a controlled biaspressure and is obtained from the air-bleed valve 53. If the portv 61.were completely closed by the needle valve 56, the pressure within thecavity 41 would be the same as, that within the air-intake manifold 39by virtue of the connection through; the port 60 which is below thethrottle valve 52. Conversely, if the port 61 is open slightly, air atatmospheric pressure is permitted to flow into the cavity 58' and thepressure within the servomotor 14 is somewhat greater than. that. withinthe air-intake manifold 39s Ina preferred. example, the bias pressurewithin theservomotor 14 isset' by the needle valve'56 at a value ofapproximately two to three. inches of mercury higher than manifoldpressure.

The force due to the differential pressure developed across thediaphragm 4-2- is transmitted through the plunger 43 which acts againstthe head of screw 35' and connecting shaft 24' tending to increase orenrich the output ofthepumpll. When the'throttle valve 52 is opened, theedge of the throttle valve blade passes beyond the port 61 and thepressure at the ports 60 and 61 becomes substantially equal to thepressure within the air-intake manifold 39. The: pressures now existingon each side of the diaphragm 42' are equal and no bias. force isexerted on. the servomotor 13. The diaphragm 32 of the servomotor 13'thereafter moves directly under the influence of manifold pressure untilthe throttle valve 52 is again closed. It is important to note that thebias force developed by the servomotor 13 is developed only duringclosed throttle condition and has no effect at all ur ng Qpen. throttl qnditiq During'deceleration, with the throttle valve closed, the pressurewithin. the air-intake manifold is less than at. idle condition, and thedifferential pressure across the diaphragm 32 is greater than at idle.The effective area of the diaphragm 32 of servomotor 13 preferably islarger than the eifective area of the diaphragm 42 of the servomotor 14.The force due to the differential pressure across the diaphragm 32,therefore, is sufficient to overcome the bias force exerted by theservomotor 14 so that the cam 20 is moved to a position for reducing theoutput of the pump 11.

There has been described by this invention an improved control mechanismfor a fuel injection system that tends to enrich the output of a fuelinjection pump during idle or closed throttle condition and the effectof which is completely removed from the system during open throttlecondition.

It is to be understood that the invention is not to be limited to thespecific constructions and arrangements shown and described, except onlyinsofar as the claims may be so limited, as it will be understood tothose skilled in the art that changes may be made without departing fromthe principles of the invention.

I claim:

1. In a control mechanism for a fuel metering device for supplying fuelto an internal combustion engine having an air-intake manifold and anair-throttle valve for controlling the flow of air into the manifold,the combination of a movable cam connected to the metering device forcontrolling the fuel output thereof, a manifold pressure responsiveservomotor connected to said cam and adapted to move it in response tochanges in manifold pressure, and an idle enrichment servomotor alsoconnected to said cam and'connected to a port adjacent the air-throttlevalve and eifective to exert a bias force on said cam during idle orclosed throttle condition proportional to the pressure developed at saidport for tending to increase the output of the device and being operableupon slight opening of said air-throttle valve to remove said biasforce.

2'. In a control mechanism for controlling the output of a fuelinjection pump adapted to supply metered charges of fuel to an internalcombustion engine having an air-intake manifold and an air-throttlevalve for controlling the admission of air into the intake manifold, thecombination of a movable element connected to control the output of thepump, a manifold pressure responsive servomotor connected to saidelement and adapted to 'move it in response to changes in manifoldpressure, and

a second servomotor also connected to said element for exertingv alimited force on it during closed throttle condition of saidair-throttle valve, said, second servomotor being connected to beresponsive to pressure developed at a point adjacent the air-throttlevalve to said air-intake manifold, the pressure being eifectiv'etooperate said second servomotor during closed throttle condition andbeing removed with slightly open throttle condition.

3. In a control mechanism for a fuel injection pump adapted to supplyfuel to an internal combustion engine having an air-intake manifold andan air-throttle valve for controlling the passage of air into themanifold, the combination of a movable cam connected to the pump forcontrolling its output, a manifold pressure responsive servomotorconnected to said cam for moving it in re sponse to changes in manifoldpressure, a second idle pressure servomotor comprising a flexiblediaphragm and a movable plunger carried-by said diaphragm and adapted toexert a limited force on: said cam during" closed throttle condition,means for applying. manifold pressure to one side of said diaphragm, andmeans for applying a different pressure on the other side" ofsaiddiaphragm includng an Conduit; connected to a port adjacent the air-.-

throttle valve, and said last-named means being effective upon openingof said throttle valve to, equalizethe pres sure on both sides of; saiddiaphragm andthereby remove the force exerted by the plunger on saidcam.

4. In a control mechanism for a fuel injection pump adapted to supplyfuel to an internal combustion engine having an air-intake manifold andan air-throttle valve for controlling the flow of air into the manifold,the combination of a movable cam connected to the pump for controllingits output, a casing, a flexible diaphragm mounted in said casing, and amovable plunger carried by said diaphragm and adapted to exert a forceon said cam, means including a conduit connected to a port in theairintake manifold for applying manifold pressure to one side of saiddiaphragm, and means for applying a differential pressure to the otherside of said diaphragm, said last-named means including a conduitconnected to two ports adjacent the air-throttle valve with one portabove and one below the air-throttle valve, and an adjustable valve forpartially restricting one of the ports for controlling the magnitude ofthe differential pressure.

References Cited in the file of this patent UNITED STATES PATENTS2,623,510 Scheweizer Dec. 30, 1952 2,708,919 Wellington et a1 May 24,1955 V 10 2,922,630 Stoltman Jan. 26, 1960 FOREIGN PATENTS 645,993 GreatBritain Nov. 15, 1950

